This invention relates to regulated power supplies and, more particularly, the use of a standby mode and an active mode of regulation in a power supply employing two separate sources of power arranged in series.
Regulated power supplies are employed in numerous applications for maintaining a steady source of voltage for use in providing power, particularly, to electronic circuits. As is well known, electronic circuits may be sensitive to the magnitude of a line voltage resulting in variation of an output signal of the circuit due to a variation in the line voltage. Such disturbances in the output signals of electronic circuits, such as electronic circuits employed in biological measurements can result in a possible mis-diagnosis of a person's ailment, by way of example. Of course, there are many other situations in which a variation in a signal measurement caused by a perturbation of line voltage can have a deleterious effect.
While numerous circuits are available for the construction of regulated power supplies, they have been implemented under constraints wherein a regulating element, such as a power transistor, is placed in an output line of the power supply with the result that regulation circuitry which controls the power transistor must be configured to operate essentially between output terminals of the supply and through a much larger voltage than may be desired. In addition, it may be difficult to develop the desired control signal for the power transistor in the situation wherein one terminal thereof is at an output terminal of the supply. As a result, control of the output voltage may not be attainable as readily as desired.